It was once commonly believed that the brain controlled it. The commander of our bodies, it is widely considered to be our overlord, dictating what everything else should do while thinking noble thoughts or, in my case, daydreaming. It was something to do.
As time and research progressed, it became clear that this was not the case. It has become clear that our brains are not just a series of slimy ropes sending electrical impulses and coldly directing our organs, muscles and tendons, but rather communicating with them. Especially our intestines.